Picture element with 2x media query

A optimized JPG with 30% quality will be used for high density screens (starting at 192dpi/2dppx).
This reduces the file size by half (162 KB instead of 368 KB at 2560px width = 56% savings).

Notes

• IE 9+ only supports dpi min-resolution instead of dppx, so 192dpi is used for the 2x media query
• -webkit-min-device-pixel-ratio is required for iOS 7.1+ and Android 4.1+

Source: Can I use Media Queries: resolution feature

Browser support

• Chrome 38+ (also for Android)
• Opera 25+
• Firefox 34+ (optional, must be enabled via browser settings)

Source: Can I use Picture element

For other browsers a JavaScript fallback is provided by Picturefill.